This application claims the benefit of U.S. provisional application Ser. No. 60/319,457, filed Aug. 9, 2002, which is incorporated herein in its entirety.
1. Field of the Invention
The invention relates generally to latches for rollup-type truck cargo doors. In one aspect, the invention relates to a cam-type door latch having an adjustable latch assembly to adjust the closing force of the door.
2. Description of the Related Art
Trailers for semi-tractors and delivery trucks have long used roll-up doors to control access through a rear opening of the truck or trailer. The doors are typically provided with a resilient gasket along the lower edge to provide a seal between the door and adjacent frame when the door is closed. The doors are typically secured in the closed position through a latch assembly which is mounted adjacent the lower edge of the door. One such latch assembly is known in the industry as a xe2x80x9ccam lock.xe2x80x9d The cam lock typically comprises a pivoting handle attached to a latch arm having a curved finger-like cam extending transverse to the arm. The cam is positioned snuggly beneath a cam retainer mounted in a catch box or latch plate mounted in the frame. Pivoting the handle downward rotates the cam into engagement with the pin, securing the door in the closed position with a downwardly-exerted force sealing the gasket against the frame. Pivoting the handle upward disengages the cam from the pin so that the door can be opened.
Over time, the gasket can wear and lose its resiliency, or the door-mounting hardware can become loosened, so that the cam lock is unable to exert sufficient force against the pin to satisfactorily draw the door downward against the frame. Various methods have been proposed for addressing this problem. Replacement of the gasket and/or adjustment of the door can correct the problem but can be time-consuming and costly. Repositioning of the cam lock on the door can also be done, but this may require a costly modification to the door. Furthermore, where the cam lock should be repositioned in order to provide the desired seal may not be immediately evident, necessitating several repositioning attempts.
Adjustable latches have also been developed. For example, U.S. Pat. No. 5,692,788 to Costa, issued Dec. 2, 1997, discloses a catch box with an adjustable locking pin for a cam-type door latch assembly. The locking pin is housed in a frame-mounted catch box into which the cam is received. The locking pin comprises a vertically-adjustable strike pin which can be adjusted upwardly or downwardly by turning a threaded post while the cam engages the strike pin, thereby ensuring the desired degree of sealing force between the door and the frame. However, the catch box is susceptible to the accumulation of dirt and debris which can interfere with the turning of the post and the movement of the strike pin, thereby limiting the adjustability of the locking pin.
A truck has a support bed at a rear portion thereof, and a rear enclosure mounted to the support bed and defined in part by sidewalls and a top wall. A door opening is at a rear portion of the enclosure and is defined by a door frame and the support bed. Vertical tracks are mounted in the door frame adjacent to the opening, and a door is mounted in the vertical tracks for vertical movement between a closed position and an open position. A latch is pivotally mounted near the bottom of the door for movement between a latched position and an unlatched position and has a handle, a cam arm, and a cam. An opening is in the support bed beneath the door opening and is adapted to receive the cam when the handle is rotated from an unlatched position to a latched position. A cam retainer is mounted in the support bed and is adapted to engage the cam and draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. According to the invention, the cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed.
According to another embodiment of the invention, the cam arm comprises a sleeve having a channelway therethrough and a shaft adapted for slidable register with the channelway. According to another embodiment, the invention further comprises a wedge nut adapted for slidable translation relative to the shaft. The wedge nut can be wedge shaped, and can have ribs to grip the channelway. According to another embodiment, the shaft and the channelway can have a wedge-shaped cross-section. According to another embodiment, the sleeve can have a lock screw to lock the shaft to the sleeve. The shaft can have notches to indicate its position relative to the sleeve.
According to another embodiment of the invention, a door is adapted to be mounted in tracks in a door opening for vertical movement between a closed position and an open position. A latch is pivotally mounted near the bottom of the door for movement between a latched position and an unlatched position and has a handle, a cam arm, and a cam. The cam is adapted to engage a cam retainer mounted in an opening in a support bed beneath the door opening to draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. The cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed.
According to yet another embodiment, a latch is adapted to be pivotally mounted near the bottom of a door for movement between a latched position and an unlatched position and having a handle, a cam arm, and a cam. The cam is adapted to engage a cam retainer mounted in an opening in a support bed beneath the door to draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. The cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed.